Not applicable.
1. Field of the Invention
The present invention relates to an adjustment mechanism and more particularly to an adjustment mechanism suitable for adjusting an office chair seat where the adjustment mechanism includes torque limiting and anti-loosening features and is inexpensive and simply constructed.
2. Description of the Related Art
Adjustable chairs are known in the art as exemplified by office type chairs disclosed in U.S. Pat. Nos. 5,755,488, 5,765,804 and 5,971,484. Nevertheless, such chairs are expensive, overly complicated and at times unreliable. Often such chairs have adjustable seats and/or backs using friction engagement to retain an adjusted position. These mechanisms, however, tend to be unreliable, expensive or difficult to manipulate or all three.
The difficulties encountered by the previous devices have been overcome by the present invention. What is described here is an adjustment mechanism for locking and unlocking two relatively movable parts, the mechanism comprising a fastener with a key element, a first structure having a key element complementary to the key element of the fastener and a second structure having a key adapted to engage a complementary key element of one of the two relatively movable parts to prevent the second structure from moving, the first and the second structures including elements for allowing relative movement of the first and second structures in a first direction at a first torque level and in a second direction at a second higher torque level.
There are a number of advantages, features and objects achieved with the present invention which are believed not to be available in earlier related devices. For example, one advantage is that the present invention provides a horizontally adjustable chair scat which is simply constructed and easily manipulated. Another object of the present invention is to provide an adjustable chair seat which is reliable. A further feature of the present invention is to provide a chair seat adjustment mechanism that is easily formed and simple to assemble.
A more complete understanding of the present invention and other objects, advantages and features thereof will be gained from a consideration of the following description of preferred embodiments read in conjunction with the accompanying drawing provided herein. The preferred embodiments represent examples of the invention which are described here in compliance with Title 35 U.S.C. section 112 (first paragraph), but the invention itself is defined by the attached claims.